Checking Month Ends in Pandas After Deprecation of Day.is_month_end

Data Offsets in Pandas

Common data offset classes include Day, Week, MonthBegin, MonthEnd, Year, etc.
They enable you to shift dates a specific number of periods (e.g., adding 2 business days, subtracting 3 months).
Data offsets are objects used to represent increments of time, like days, weeks, months, or years.
Pandas provides tools for working with time series data, including dates and times.

pandas.tseries.offsets.Day.is_month_end

In earlier versions, it always returned False.
It was intended to check if a Day offset (representing a single day) falls on the end of the month for a given timestamp (ts).
This method, however, is deprecated in Pandas versions 1.0.0 and later.

Alternatives for Checking Month Ends

Since Day.is_month_end is deprecated, there are more reliable ways to determine if a date is at the month's end:

Using Day offset with onOffset

import pandas as pd

offset = pd.offsets.Day(1)  # Create a Day offset
date = pd.to_datetime('2024-07-31')  # Example date

# Check if the date + 1 day (to ensure it lands on the month end) is on the offset
is_month_end = offset.is_on_offset(date + offset)
print(is_month_end)  # Output: True

Here, we create a Day offset (offset) and add it to the date (date) to potentially land on the month's end. Then, we use is_on_offset to verify if the adjusted date is indeed a valid offset (i.e., the last day of the month).

Using MonthEnd offset
```
offset = pd.offsets.MonthEnd(0)  # MonthEnd offset (0 for current month)
date = pd.to_datetime('2024-07-31')

is_month_end = offset.is_on_offset(date)
print(is_month_end)  # Output: True
```
This approach directly employs the MonthEnd offset, which inherently represents the last day of the month. We use is_on_offset to confirm if the given date aligns with this offset.

Choose the method that best suits your use case, depending on whether you want to check if a single day offset lands on the month end (method 1) or directly use a month-end-specific offset (method 2).

Using Day offset with onOffset (recommended)

import pandas as pd

def is_month_end_using_day_offset(date):
  """Checks if a date is at the month's end using Day offset and onOffset."""
  offset = pd.offsets.Day(1)  # Create a Day offset
  return offset.is_on_offset(date + offset)  # Check if date + 1 day is on offset

# Example usage
date_str = '2024-08-31'  # Example date (August 31st)
date = pd.to_datetime(date_str)

is_month_end = is_month_end_using_day_offset(date)
print(f"Is '{date_str}' the end of the month? {is_month_end}")

This code defines a function is_month_end_using_day_offset that takes a date and returns True if it's the end of the month. It creates a Day(1) offset, adds it to the date, and checks if the adjusted date is on the offset using is_on_offset.

Using MonthEnd offset

import pandas as pd

def is_month_end_using_monthend_offset(date):
  """Checks if a date is at the month's end using MonthEnd offset."""
  offset = pd.offsets.MonthEnd(0)  # MonthEnd offset (0 for current month)
  return offset.is_on_offset(date)

# Example usage
date_str = '2024-07-31'  # Example date (July 31st)
date = pd.to_datetime(date_str)

is_month_end = is_month_end_using_monthend_offset(date)
print(f"Is '{date_str}' the end of the month? {is_month_end}")

This code defines a function is_month_end_using_monthend_offset that takes a date and returns True if it's the end of the month. It creates a MonthEnd(0) offset (representing the end of the current month) and uses is_on_offset to check if the given date aligns with this offset.

Using Day offset with is_on_offset

This approach checks if a single-day offset (one day ahead) lands on the month end:

import pandas as pd

def is_month_end_using_day_offset(date):
  """Checks if a date is at the month's end using Day offset and onOffset."""
  offset = pd.offsets.Day(1)  # Create a Day offset
  return offset.is_on_offset(date + offset)  # Check if date + 1 day is on offset

# Example usage
date_str = '2024-08-31'  # Example date (August 31st)
date = pd.to_datetime(date_str)

is_month_end = is_month_end_using_day_offset(date)
print(f"Is '{date_str}' the end of the month? {is_month_end}")

Using MonthEnd offset

This method directly utilizes the MonthEnd offset, which inherently represents the last day of the month:

import pandas as pd

def is_month_end_using_monthend_offset(date):
  """Checks if a date is at the month's end using MonthEnd offset."""
  offset = pd.offsets.MonthEnd(0)  # MonthEnd offset (0 for current month)
  return offset.is_on_offset(date)

# Example usage
date_str = '2024-07-31'  # Example date (July 31st)
date = pd.to_datetime(date_str)

is_month_end = is_month_end_using_monthend_offset(date)
print(f"Is '{date_str}' the end of the month? {is_month_end}")

For a more direct and clear way to check for month ends, use the second approach (MonthEnd offset).
If you specifically need to check if a single-day offset falls on the month end, use the first approach (Day offset with is_on_offset).